Microfilm projector



June 5, 1945. A BERGLUND 2,377,476

MICRO FILM PROJECTOR Filed May 15, 1943 6 Sheets-Sheet l lP NENTOR vGUSTAVIARTHUR BERGL ND BY (v/ I) ATTORNEY June 5, 1945. A, BERGLUND2,377,476

MICRO FILM PROJECTOR Filed May 15, 1943 6 Sheets-Sheet 2 INVENTOR GUSTAVARTHUR BE RGLUND ATTORNEY 6 Sheds-Sheet l? G. A.'BERGLUND mono FILMPROJECTOR Filed May 15, 1943' FIG.3

June 5, 1945.

June 5, 1945. A, BERGLUND 2,377,476

MICRO FILM PROJECTOR Filed May 15, 1943 6 Sheets-Sheet 4 FIG.9. :20 129'K 20 '23 I ATTORNEY June 5, 1945. A, BERGLUND 2,377,476

MICRO FILM PROJECTOR Filed May 15, 1945 e Sheets-Sheet s INVENT'OR USTAVARTHUR BERGLUND June 5, 1945. G; A. BERGLUND MICRO FILM PROJECTOR FiledMay 15, 1943 6 Sheets-Sheet 6 FIG].

GUSTAV ARTHUR BERG LUN D Patented June 5, 1945 UNITED STATES PATENTOFFICE 9 Claims.

This invention relates to projectors for showing photographs made oncontinuous transparent strip film, and more particularly relates to thattype of 'film projector which is employed to examine photographs ofdocuments which have been recorded on 16 mm. negative fllm.

The present invention-resides in the provision of a film gate openingstructure, which opens the gate before the film may be moved in eitherdirection. The invention also provides means for rotating the image on atranslucent or other type of screen without moving the film or the filmsupporting structure. In further detail, separate controls are providedfor rotating the image, focusing the image, and locking open the filmate. 1" 8 An object of the invention is to obtain a brightly illuminatedfull size image of a previously photographed document in aself-contained projector box which may be viewed in a. room lighted withordinary illumination.

Another object of the invention is to enable the operator to rotate theimage of the document photographed by turning a small knob located at aconvenient point on the projector assembly.

Another object of the invention 15 to diminish the probability ofscratching the film by accidentally pulling it through a film gate whichhas not been opened.

Another object of the invention is to facilitate more rapid location ofphotographed documents on a roll of film.

In the drawings:

Fig. 1 is an isometric view of the entire machine;

' Fig. 2 is a cross sectional view taken from the right as shown in Fig.1 and shows the lamp housing in elevation with the reflector and box incross section;

' Fig. 3 is a top view of the projector, with parts of the top brokenaway to show the details of the film gate opening structure;

Fig. 4 is a detail isometric view of the mechanism which pulls the filmthrough the gate and holds the gate open during this operation;

Fig. 5 is an enlarged cross sectional view of the lamp housing and lenssystem taken through the center of the machine viewed from the right asshown in Fig. 1.

Fig. 6 is a cross section taken on line 6-6 of Fi 5.

Fig. 7 is a bottom plan view of the gate support and associatedstructure shown in Fig. 6 with the lower lens omitted.

the base. A projector screen i2 is positioned in front wall II and isheld by an appropriate frame l3. Frame I3 is hinged to front wall II atthe bottom and has a latch at the top holding the screen in closedposition.

Box H) has top plate I mounted about its margins in a seat formed in theside, front and back walls as shown in Fig. 2.

A gate housing 2 is mounted over a central opening in top plate I andhas a seat 3 formed about an opening in registry with the opening in topplate I for receiving gate support 58 suspended through said openings asshown in Fig. 5. A wall I of said gate housing is provided withprojections to form bearings for shafts H2 and I l 5 and to supportpulleys H6.

Lateral flange 5 about the top and end edges of wall 4 providecompartment I! closed by and accessible through cover 6 secured to therear edge of said flange.

A lamp housing It is mounted on lateral flange 5, contains lamp l5 (seeFig. 5) and a series of lenses forming a light condensing system i6.Directly beneath lamp housing It is a compartment l1 formed by wall 4,flange 5 and back cover 6 housing mechanical means for rotating twospools Is and 20 on which-a fllm 2| i wound.

A crank 22 at the right-hand side of the box is used to move the filmfrom one spool to the other passing through film gate 23. The film gate23 is composed of two pieces of glass, one of these is a stationaryfixed plate 24, while the second is a vertically movable plate 25. Plate24 is secured by plates 29 to gate support 58. As indicated in Figs. 2,4 and 5, the two plates hold film 2| securely in place by means of aresilient mounting hereinafter to be described in detail.

When the operator first turns crank 22, the first movement of about 20lowers plate 25 so that the film may run free. Subsequent motion of thecrank will move the film through the gate in either direction asdesired. When the handle is released by the operator, the resilientmounting presses plate 25 upwardly and again clamps the film in thefocal plane of the lens.

On the top plate of the projector near the forward edge is a focusingknob- 26. This knob communicates its motion by means of a sprocket chainto a sprocket wheel 27 (see Fig. Also on the top plate of the projectorcase is a knob 28, which is used by the operator to rotate the image onthe screen l2. The details of this operation will be hereinafterdescribed. A third knob 30 may be used by the operator to hold the gatepermanently in an open position and is used when the film is adjusted orwhen the film is inserted or removed. A small notch 3i (see Fig. 2) iscut in the shaft of knob 30 so that the operator may depress the knoband push it forward a. small amount, thereby latching it in itsdepressed position. After the film has been adjusted, the gate may beclosed by pulling the knob toward the observer, and it will snap backinto place again.

A large glass mirror 32 is positioned in the interior of box H] toreflect the rays of light from the optical system toward screen I 2,where the resultant image is produced. The mirror 32 is detachablymounted on suitable brackets 33 secured to the sides of box [0.

The source of light for the optical system, as has already beenindicated, is the tungsten filament light i5, which is supported in abayonet socket 45 firmly secured to the base of lamp housing i4. Behindthe lamp is a silvered lens 45,.

which acts in the same manner as a spherical reflector unit. Thesilvered lens 46 receives light from the lamp filament and reflects itback on the filament itself, in a manner well known in the art.

A condenser lens 4! forming part of system i5, is positioned directly infront of lamp l5 to render the rays of light approximately parallel.This condensing lens generally has a fiat surface on one side and aparabolic surface on the other side. After being converted to parallelrays the light strikes mirror 48, which is silvered on its frontsurface, This mirror is inclined at an angle of 45 so that the lightreflected therefrom will proceed vertically downward to lens barrel 50mounted in the lamp housing base and also forming part of system It. Atthe upper end of barrel 50 a plain piece of heat absorbing glass 5! isinterposed to keep as much heat out of the lens system as possible.

The light next passes through two condenser lenses 52 and 53,which'focus the parallel beam from mirror 48 to a focus which isapproximately at the center of a projection lens 54. The projection lens54 may be any good quality photo graphic lens. The one shown in Fig. 5is a three element lens, one component of which is a doublet. Betweencondensing lens 53 and projection lens 54 the light passes through thetwo plates 24 and 25 of film gate 23 and film 2i, and the opticalarrangement must be such that the complete film is illuminated by thecondensed light beam.

After leaving projection lens 54 the light enters a Dove prism 55. Asthe light enters the entrance face, it is refracted toward thehypotenuse side 55. This side is generally silvered so that a reflectionwill always occur here and the light will then proceed through the exitface 51, where it is again refracted and proceeds in a generallydownward direction. The large size of the prism, as indicated in Fig. 5,is necessary because the rays of light, as they leave projection lens54, will spread out to enclose a considerable angular field, therebyusing almost the entire exit face 51 as they emerge.-

Since the entrance and exit faces of the Dove prism are inclined at anangle of to the axial rays, the light rays passing through the prismshould be parallel, That is, the individual pencils should be focused atinfinity to avoid astigmatic distortion. In order to attain such acondition lens (it is adjusted so that the film is in the focal plane.Then another lens 51A mounted on and below prism carrier II is placednear the prism exit face to render the rays convergent and cause them tobe focused on screen I2.

The Dove prism is employed solely as a means of rotating the image onthe screen. This phenomenon is well known in the art of geometric opticsand has been used in submarine periscopes and other vertical telescopicsights. One half turn of the Dove prism 55 will result in a completerotation of the image on screen l2 Gate support 58 is used to mount thefilm gate 23. Support 58 has a plate formed with tubular extensioninternally threaded at 6i. A plate supporting tube or member 82 has aflange 83 at the bottom thereof and is slidable on the outside ofextension 50. This flange is engaged by lever member or rock lever 64 inthe opening and closing movements of the gate as hereinafter described.The bottom plate 25 of film gate 23 is supported in tubular housingbolted to tube 52 through slots in extension 80 and moves up and downwith tube 52.

Tubular housing slidably engages in and extends through an aperture ingate support 58 as shown in Fig. 5. Tension springs 59 secured at oneend to plate supporting tube 82 and at the other end to the underside ofsupport 58 normally hold plate 25 in an upper position to engage andhold the film against stationary plate 24. Lever arms 84 are mounted inspaced parallel relation on pivot rod 64' rotatable in bearingsdepending from bearing frame 83' carried by top Plate I.

A focusing tube 86 is threaded in threads ii of extension 50. Sprocketwheel 21 is mounted on the lower end of focusing tube 55. The upper endof tube 66 is provided with an end wall 65' carrying a reducedcylindrical extension 65" in axial alignment therewith.

A prism carrier H of cylindrical tubular form is slidably mounted withinfocusing tube 56. Prism carrier H has an end wall II engaging end wall55' of focusing tube 66 and a reduced cylindrical extension 'H"projecting upwardly therefrom and rotatably engaged in cylindricalextension 56". Tubular extension 'H" is internally threaded as shown inFig. 5 for threadedly receiving and mounting coupling member 61.Coupling member 61 secures prism carrier H to focusing tube 66 forrotation therein. Coupling member 81 also carries-the projection lensassembly 54.

A prism bracket 68 is detachably secured to the lower end of prismcarrier 1i and has Dove prism 55 secured thereto by clips 10 and 10'.The lower end of prism carrier 1| extends below the lower end offocusing tube 56 and has sprocket 12 mounted on the lower end thereof.An endless chain 13 is mounted on sprocket 12 of prisni carrier H andsprocket 14 on the lower end of knob 28 so that upon manual rotation ofknob 28 sprocket wheel I2 will be rotated to turn prism carrier H andprism 55 for rotating the position of the image on screen II. The prismmay be rotated in either direction and to any desired extent.

top wall of box I in a position to engage a. portion of the chainengaged over sprockets 12 and M. This brake has two brake members and11. Brake member 18 is in the form of a bracket having a lateralextensional: one end secured to the underside of the top wall of box I0.Brake member 11 has a lateral extension at one end for engaging brakemember I8 in order to hold the brake members in spaced relation at oneend while the opposite ends are free to move toward and away from oneanother.

Brake member I8 carries a pair of guide pins I8 slidably supportingbrake member 11 having openings to receive the pins. Coil springs 18 areengaged over pins I8 between heads on the outer free ends thereof andbrake member 11 for normally urging brake member 11 toward brake member18. The side edges of each brake member throughout the portions thereofthat engage opposite sides of the chain are curved outwardly away fromeach other in order that the chain will Prism carrier 1| is held inadjusted position by brake against rotation during operation of grooveson the shaft. A floating ratchet I04 is mounted for free movement onshaft 88 between gears MI and I02. The movement of ratchet I04 iscontrolled by pin I08 which works in slot I08 cut in the periphery ofratchet wheel I04. The slot I08 is out so that in rotation shaft 88 willmove pin I08 to cam the ratchet wheel toward the rear of the machine ifthe motion is counter-clockwise and toward the front of the machine ifthe motion is clockwise.

- A pin I0! is mounted on the inside face of sprocket wheel I02 and asimilar pin I08 is attached to the inside face of sprocket wheel IOI.These two pins are arranged for engagement by the teeth of ratchet wheelI04 so that, when shaft 88 is turned in one direction by handle 22, oneof the sprocket wheels will be turned while the other is leftstationary. Reversing the motion of crank 22 will disengage the ratchetwheel from one of the sprocket wheels and cause it to engage the other.This ratchet wheel structure operates so that the film is pulled throughthe film gate by operating the spool on which the film is wound whilethe other spool idles.

Sprocket wheel IOI operates chain IIO to rotate sprocket wheel IIIdirectly'connected to shaft II2 carrying means for detachably securing afilm spool "thereon. Sprocket wheel I02 operfocusing knob 26 forrotating focusing member 88.

The film 2I is wound from one film spool to the other by operatinghandle 22. This handle is' secured to a shaft journaled in theright-hand side of the box which mounts sprocket wheel on the inside ofthe box. A chain 8i is engaged over sprocket wheels 80 and 82. Sprocketwheel 82 is secured to one end of shaft 88 rotatably mounted in bearingframe 88 secured to the underside of top plate I of the projector. Abevel gear 84 is secured at the other end of shaft 88. This gear mesheswith another similar gear freely rotatable on cross shaft 86. Shaft 88is rotatably mounted in frame 83.

Two clutch plates 81 and 88 are mounted on shaft 83, plate 81 beingrigidly attached while plate 88 is,slidable and prevented from turningon the shaft by means of rods 88 slidably engaged in collar 88. Twoleather or felt washers 80 and 8| are positioned against the inner facesof clutch plates 81 and 88 and between these washers is placed a thickcircular gate actuating or cam disc 82 with a wide slot 83 cut in oneside thereof.

which is moved by disc 82 to open the film gate and release the film. Inorder to provide the proper frictional drag between the clutch platesand gate operating disc 82, a spring 85 is positioned about shaft 83between slidable clutch plate 88 and collar 88. Collar 88 is firmlysecured to shaft 83 by means of a suitable set screw.

A cylindrical member 81 is secured to shaft 85 and has a wide slot 88cut in the periphery thereof. A tongue I00 extending from mitre gear 85engages in slot 88. The slot 88 is approximately twice as wide as tongueI00 and. therefore. considerable back-lash or lost motion always resultswhen a turning force is transmitted by means of this mechanism. Thepurpose for this lost motion the rear end of shaft 88 and held fromtransverse motion by set screws I08 fitting into circular ates sprocketchain II8 to rotate sprocket wheel III and shaft II8 for turning theother film spool I8. Two pairs of idler pulleys II8 are mounted onopposite sides of the film gate for receiving and guiding th filmthrough the film gate.

When the operator turns the handle 22 the immediate result is theturning of shaft 83 and the partial rotation of disc 82, which raisesrod 84 to operate lever 88 in a direction to push down on platesupporting tube 82 thereby separating lower plate 28 of film gate 23from upper plate 24. The movement of rod 88 is restricted to such anextent that disc 82 cannot continue more than one-eighth of a revolutionin either direction. and, therefore, after this initial motion, it willcease to revolve and discs 81 and 88 will continue to move by slippingover washers 80 and 8|. The

dimensions of slot 88 and tongue I 00 are such that the rotary motion istransferred to shaft 86 about the time film gate 28 is fully opened.Then rotation is given to either one of the sprocket wheels I M and I02and its associated film spool I8 or 20 willie be rotated to pull thefilm through the open ga a If theoperator now stops rotatinghandle 22,but holds it in place, the film will stop moving, but gate 28 will notclose. It is necessary to either remove the hand from crank 22 or elseallow the crank to move back a short distance so that the gate willclose and bring the film again into the focal plane of the projectionlens. This backward motion is obtained by the tension of springs 58pulling plate supporting tube 82 upwardly and operating lever 88 toreturn disc 82 to a position where rod 88 seats at the bottom slot 93.This small backward motion is just suflicient to move tongue I00 intothe center of slot 88, so that the film may subsequently be moved ineither direction with the initial conditions of alignment al wayspresent. In order to put a brake on the film spools so that they willstop after a fast motion of the film, two spring brakes III anchored topins II8 are placed around brake pulleys II8 rigidly secured to filmshafts H2 and H5. v

A modified form of film drive is shown in Figs. 8 to 10. A shaft I20 isrotatably mounted in hear ing frame 83' .in place of shaft 88 andcarries the bevel gear I2I rigidly mounted thereon in mesh with bevelgear 84 so that in the rotation of shaft shaft I20 will besimultaneously rotated. rockets I22 and I23 are rotatably mounted onwaft I20 adjacent one of the bearings of bearing irame 83. Thesesprockets are in spaced relation on opposite sides of clutch collar I24rigidly secured to shaft I20 by set screw I25. Clutch collar I24 carriesaslidable clutch pin I28 extending in transverse relation and formedwith beveled ends I21. Clutch teeth I28 are formed on sprockets I22 andI23 to'provide a shoulder for engagement with the ends of clutch pinI26. The shoulders on one sprocket extend or face in the oppositedirection to the shoulders on the other sprocket. Clutch teeth I28 alsohave cam faces for engagement with the inclined faces I21 on the ends ofclutch pin I26.

A compression spring I29 is engaged between sprocket I23 and collar I30secured on the end of shaft I20 for normally moving sprocket I23 towardssprocket I22 and clutch collar I24.

With this film drive construction chains H0 7 and II! are engaged oversprockets I22 and I23 respectively, for driving spindles H2 and H5according to the direction of rotation of shaft I20.

When handle 22 is rotated in one direction it will rotate shaft I20 inone direction thereby rotating clutch collar I24. Rotation of clutchcollar I24 will cause cam face I21 on one end of clutch pin I26 toengage the cam face on the clutch teeth I28 of one of the sprockets forproducing end-wise movement of clutch pin I28 so that the opposite endwill engage the shoulder of clutch teeth I28 on the other sprocket. Thiswill cause rotation of the sprocket having the clutch pin engaged withthe shoulder of a clutch tooth I28 thereon and result in driving one ofthe spindles. There is a certain amount of lost motion in the drivebetween the spindles and the rotation of handle 22 so that film gate 25will be moved to the open position before clutch pin I26 engagestheshoulder of clutch teeth I28 for driving one of the sprockets.

When handle 22 is rotated in the opposite direction the slidablemovement of clutch pin I26 is reversed and the other sprocket is drivenin a manner that will be clear from the foregoing description. SpringI29 allows for end-wise movement of sprocket I23 to compensate for anybinding action, should any take place between clutch teeth I28 on thetwo sprockets during the shifting movement of clutch pin I26. This typeof film drive mechanism is found to be very satisfactory in theoperation of the projector to give sufficient lost motion for theopening movement of film gate 25 before clutch pin I26 engages clutchteeth I28 to wind the fllrh on one of the spindles.

The tubular carrier II and focusing tube 66 are shown in Fig. 5 as beingin telescoped relation in each other and tubular extension 60, with thefocusing lens and prism in axial relation within these tubes and incoaxial optical relation to each other. The knobs provide a convenientremote control in operation of these tubes to thread the focusing tubein tubular extension 60 for focusing an image on the screen while one ofthe knobs may be rotated for rotating carrier II within focusing tube 66to rotate the position of an image on the screen into reading position.This provides a very compact unit which can be made with precision insuch a manner that all parts of the lens system for protecting thelight, holding the film and focusing the image together with the controlof this position are mounted in fixed relation to each other on the topplate in order that an efficient construction can be made economicallyto obtain the desired results in the projection of film for reading onthe screen.

It will be noted that the friction drive for gate actuating disc 92provides an efilcient means for moving the film gate into open positionduring the feeding of film through the gate. The tension on clutchplates 81 and 88 may be varied by controlling the position of collar 96on shaft 83. By this means the desired amount of friction drive can beobtained for disc 82 to secure efficient operation of the movable plateof the film gate to open position.

It will be understood that with either form of film drive clutchmechanism illustrated in the drawings, the clutch collar or the clutchpin is shifted back and forth longitudinally axially of the shaft forselectively driving one of the spindles. The lost motion occurring inthe shifting of the clutch before engagement with one of the sprocketwheels to feed film allows movable plate 25 to be first moved into openposition.

The invention claimed is:

1. A projector, comprising a box, a top plate secured to and forming thetop of said box, a gate support fixed in position on said top plate andhaving a tubular extension, 9. film gate having stationary and movableplates, said stationary plate being secured to said gate supportperpendicular to the axis of said extension, a tubular housing carryingsaid movable plate longitudinally slidable in the tubular extension onsaid gate support in substantially perpendicular relation toward andfrom said stationary plate, a tubular carrier rotatably mounted in saidtubular extension and longitudinally adjustable therein, a focusing lensand image positioning prism mounted in fixed axial relation in saidcarrier, means on said top plate for mounting and feeding film throughsaid film gate operable to engage and move said tubular housing andmovable plate into open spaced relation to said stationary plate inadvance of feeding film through said gate, and manually operable meansfor rotating said carrier to focus and position an image from a filmheld by said plates in said film gate in readable relation on a screen.

2. A projector, comprising a gate support fixed on said projector andhaving a tubular extension,

a film gate having stationary and movable plates, said stationary platebeing attached to said support, a tubular housing carrying said movableplate slidably mounted in said tubular extension on said support formovement toward and from said stationary plate, a plate supportingmember slidably mounted on said tubular extension and having saidtubular housing secured thereto, a rock lever pivoted on said projectorhaving one end engaged with said plate supporting member, resilientmeans connecting said plate supporting member and gate support fornormally moving said movalble plate into closed film clamping positionagainst said stationary plate, and means for supporting and feeding filmthrough said film gate in either direction having a friction rotated camfor engaging the opposite end of said rock lever for moving it tooperate said plate support and move said movable plate into open spacedrelation to said stationary plate during feeding of film through saidfilm gate.

3. A projector, comprising a box, a gate support fixed on said box andhaving a tubular extension, a film gate formed of a stationary platemounted on said support and a movable plate, a tubular housing carryingsaid movable plate having portions slidable through an opening in saidsupport and portions slidable on said tubular extension, resilient meansnormally actuating tubular housing. a manually rotated shaft, a gateactuating disc rotatably mounted on said shaft and engaging the otherend of said lever for rocking said lever upon rotation in eitherdirection, and friction drive means on said shaft engaging said discoperable to partially rotate said disc to operate said lever and housingin the rotation of said shaft for moving said film gate into openposition with said plates separated.

4. A projector, comprising a stationary gate support formed of a plateportion having a tubular extension, 9. film gate having a stationaryplate mounted on said plate portion of said gate support and a movableplate, a tubular housing carrying said movable plate slidably mounted insaid plate portion and tubular extension, a plate supporting tubeslidable on said tubular extension and attached to said tubular housing,a lever pivoted on said projector having one end engaging said platesupporting tube, a rotatable shaft in said projector, a disc rotatableon said shaft engaging the other end of said lever for rocking saidlever on its pivot to move said plate supporting tube and tubularhousing axially on said tubular extension for moving said movable plateto open said film gate, friction drive means on said shaft engaging andoperating said disc for rocking said lever, and means for normallyoperating said plate supporting tube to hold said movable plate in filmgate closing position, said plate support-' ing tube eflectively guidingthe operation of said movable plate.

5. A projector. comprising a film gate formed of stationary and movableplates for holding a film I, therein, means for normally moving saidmovable plate toward said stationary plate, a rock lever pivoted on saidprojector having one end connected to said movable plate, a-rotary shaftfor operating film feeding means in said projector, a disc rotatable onsaid shaft having mean engaging the opposite end of said lever forrocking said lever when rotated, a pair of friction discs mounted onsaid shaft on opposite sides of said first mentioned disc, one of saidfriction discs being fixed on said shaft, means for resiliently andslidably urging the other friction disc toward .said fixed friction discwhile held on said shaft in said tubular extensiommeans for'moving saidcarrier axially in said extension, a focusing lens and positioning prismmounted in optically coaxial relation in said carrier, a manuallyoperated remotely positioned control means on said top plate connectedto operate said prism carrier axially in said extension for focusing animage from said film on a screen and another manually operated remotelypositioned control means on said top plate connected to rotate saidprism carrier for rotating the image on said screen into readingposition.

'7. A projector, comprising a top plate, a film gate carried by said topplate, a tubular extension can'ied b said top plate; a tubular carrierthreaded in said tubular extension and independently rotatable therein,a focusing lens and positioning prism mounted in optically coaxialrelation in said carrier, a rotatable knob on said top plate remote fromsaid film gate connected to said carrier for moving it on the threadedconnection with said tubular extension for focusing an image from in onto a screen, and a rotatable knob on said top plate connected to saidcarrier independent of said first mentioned knob for rotating saidcarrier in said tubular extension for rotating the image into readingposition on said screen.

8. A projector, comprising a top plate, carrying a film gate for holdingfilm to be projected 1 onto a screen, a tubular extension carried bysaid top plate, a focusing tube threaded in said extension. a prismcarrier rotatable in said focusing tube, a focusing. lens andpositioning prism mounted in said carrier in optically axial relaon saidscreen, and another manually operable means on said top plate remotefrom said extension for rotating said carrier'and prism for rotating animage on said screen into reading position.

9. A projector, comprising a top plate carrying a film gate for holdingfilm to be projected on to a screen, a tubular extension carried by saidtop plate, a focusing tube and a tubular prism carrier mounted incoaxial telescoping relation within one another and said tubularextension. said fucusing tube having a. threaded connection with saidtubular extension, means retaining said carrier rotatably engaged insaid focusing tube, a focusing lens and image positioning prism mountedwithin-said tubular carrier in optically coaxial relation, means on saidtop plate remote from said extension'and connected to said focusing tubefor threading said focusing tube in said extension for focusing an imageprojected from film in said gate'on said screen, and another means onsaid top plate remote from said extension and connected with saidcarrier for rotating said carrier in said focusing tube for rotating animage on the screen into reading noel--

